The invention relates to an engine compression brake system, and particularly, to an engine compression brake system of the type wherein the pivot center of the exhaust rocker arm is displaced.
Various types of engine compression brake systems are known. In one type of engine compression brake system, a lost motion device is included in an end of the rocker arm or in the links connecting the rocker arm to the cam lobe or valve (push rod or lifter) to allow a control mechanism to react to or ignore a portion of the cam lobe profile. Another type of engine compression brake system is shown in U.S. Pat. No. 5,647,319, issued in 1997 to Uehara et al. and U.S. Pat. No. 3,367,312, issued in 1966 to Jonsson. Both of these systems have engine brake mechanisms wherein the pivot center of the exhaust rocker arm is displaced or shifted by an eccentric which is connected to an hydraulic piston/actuator by a lever arm.
However, these mechanisms require an extra mechanical component between the hydraulic piston/actuator and the rocker arm. Also, the various actuation arms and levers of these systems are subject to tension and bending loads, which increases the probability of stress failures. These additional links, arms and actuators also increase the manufacturing tolerance requirements of many of the components. These systems also require intermediate arms, a second rocker arm eccentric bore, features on the small end of the actuation/pivot arm and features on the mechanical actuation end of the piston. These parts and features all add cost and complexity, and reduce system reliability. Finally, these systems result in an assembly which is not as compact as desired, and could result in increased engine height.